The field covers a multifunction warming device including a clinical garment with an elongate convective apparatus supported on the inside of the garment, transversely to the garment, running between its sleeves.
In this specification, use of the term “convective” to denote the transfer of heat from a device to a body refers to the device's principal mode of heat transfer, it being understood that heat may at the same time be transferred from the device to the body by conduction and radiation, although not to the degree of convection.
Convective devices that transfer heat to a human body are known. For example, there are devices that receive a stream of pressurized, warmed air, inflate in response to the pressurized air, distribute the warmed air within a pneumatic structure, and emit the warmed air onto a body to accomplish such objectives as increasing comfort, reducing shivering, and treating or preventing hypothermia. These devices are typically called “convective thermal blankets” or “covers”; for convenience, in this discussion and the following specification, they shall be called, simply, “thermal blankets.” Arizant Healthcare Inc., the assignee of this application, makes and sells such devices under the BAIR HUGGER® brand. One such device is the Model 522 Upper Body Blanket.
Thermal blankets have been specifically designed for particular deployments where therapeutic warming is indicated. Three representative thermal blankets known in the prior art are shown in FIGS. 1A-1D. A “full body” thermal blanket 10 is shown in FIG. 1A. The full body thermal blanket is adapted to lie upon a person and to extend longitudinally along the body of the person in order to cover substantially the person's entire body, from near the ankles or feet up to the neck. A “lower body” thermal blanket 12 is shown in FIG. 1B. The lower body thermal blanket 12 is adapted to lie upon the person and to extend longitudinally along the body of a person in order to cover the person's lower body, from near the ankles or feet up to the waist or pelvis of the person. An “upper body” thermal blanket 15 is illustrated in FIGS. 1C and 1D. The upper body thermal blanket 15 has a bow-tie shape that is adapted to lie upon and extend transversely across the upper body of a person in order to cover the person's chest and extended arms. A head drape 16 may be formed on or attached to the upper body thermal blanket 15 for draping over the head 17 of a person in order to retain warmed air expelled through the blanket 15 about the head to aid in therapeutic warming during surgery. When fed a stream of warmed pressurized air, each of the thermal blankets 10, 12, 15 inflates and distributes the air within itself. While the thermal blanket lies on the person, the warmed pressurized air flows through apertures or interstices in a permeable surface of the thermal blanket which faces the person. These thermal blankets may have one, two, or more inlet ports 18 through which an air hose 19 provides warmed pressurized air from a heater/blower unit (not shown in these drawings).
The construction of thermal blankets is well understood. Examples of specific constructions are given in U.S. Pat. No. 5,620,482, U.S. Pat. No. 5,443,488, U.S. Pat. No. 5,360,439, and U.S. Pat. No. 5,304,213. See also U.S. Pat. No. 5,974,605.
Clinical garments such as hospital gowns are widely used when patients remove clothes in preparation for surgery. A hospital gown provides a disrobed patient with privacy and dignity before and after surgery, and often remains on the patient throughout the surgical cycle. The utility of clinical garments has been expanded by a recent invention disclosed in the referenced Publication No. WO 2003/086500. The invention described in the publication adapts a clinical garment such as a robe or gown to receive a convective device such as a thermal blanket in order to warm a person wearing the garment in a clinical setting for comfort and mobility of the person. An invention covering a multifunction warming device for perioperative use is described in the referenced Publication US 2006/0122671 wherein a warming device is constituted of a clinical garment and a convective apparatus adapted for comfort and therapeutic warming that is supported on the inside surface of the garment.
The term “perioperative” is defined in the PDR Medical Dictionary, Second Edition, (Medical Economics Company, 2000), as “around the time of operation.” The perioperative period is characterized by a sequence including the time preceding an operation when a patient is being prepared for surgery (“the preoperative period”), followed by the time spent in surgery (“the intraoperative period”), and by the time following an operation when the patient is closely monitored for complications while recovering from the effects of anesthesia (“the postoperative period”).
According to Mahoney et al. (Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs. AANA Journal. 4/99; 67, 2:155-164.), therapeutic warming is employed during at least the intraoperative period in order to prevent or mitigate effects that result from hypothermia. In fact, it is increasingly manifest that maintenance of normothermia perioperatively enhances the prospects for a quick, successful recovery from surgery. For example, maintenance of perioperative normothermia appears to be a factor in decreasing the incidence of surgical wound infections in patients undergoing colorectal surgery, (Kurz A, Sessler D I, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Engl J. Med. May 9, 1996; 334(19):1209-1215). Other studies suggest that maintenance of perioperative normothermia improves surgical outcomes at low cost, (Harper C M, McNicholas T, Gowrie-Mohan S. Maintaining perioperative normothermia. BMJ. Apr. 5, 2003; 326(7392):721-722). The effectiveness of therapeutic warming depends upon delivery of enough heat to a patient's body to raise the patient's core body temperature to, or maintain it within, a narrow range, typically around 37° C. This range is called “normothermic” and a body with a core temperature in this range is at “normothermia.” Hypothermia occurs when the core body temperature falls below 36° C.; mild hypothermia occurs when core body temperature is in the range of 34° C. to 36° C. Therefore, “perioperative therapeutic warming” is warming therapy capable of being delivered during one or more of the perioperative periods for the prevention or treatment of hypothermia.
Therapeutic warming is contrasted with “comfort warming” which is intended to maintain or enhance a patient's sense of “thermal comfort”. Of course, therapeutic warming may also comfort a patient by alleviating shivering or a feeling of being cold, but this is a secondary or ancillary effect; and, comfort warming may have some therapeutic effect. However, even though thermal comfort is a subjective notion, environmental conditions that produce a sense of thermal comfort in a population of human beings are known and well tabulated. For example, Fanger (Thermal Comfort: Analysis and Applications of Environmental Engineering, Danish Technical press, Copenhagen, 1970) defines thermal comfort as “that condition of mind which expresses satisfaction with the thermal environment.” Even when a patient is normothermic, less than ideal environmental conditions can result in acute feelings of discomfort. Under normothermic conditions, thermal comfort is largely determined with reference to skin temperature, not core body temperature. Comfort warming is warming applied to a patient to alleviate the patient's sense of thermal discomfort.
Therapeutic warming may be indicated during any one or more of the perioperative periods. For example, for a short operation in a surgery with no warming equipment available, a person may be warmed preoperatively in a preparation area to raise mean body temperature to a level higher than normal in order to store enough thermal energy to maintain normothermia, without heating, intraoperatively. After surgery, it may be necessary to apply therapeutic warming in a recovery area to raise the core temperature to normothermia and maintain it there for a period of time while anesthesia wears off. Alternatively, for a long surgery in an arena with heating equipment available, a person may be warmed for comfort before surgery and warmed therapeutically during and after surgery.
Therapeutic warming is typically provided by convective devices such as the thermal blankets shown in FIGS. 1A-1D. An example of use of a full body thermal blanket for therapeutic warming is found in U.S. Pat. No. 6,524,332, “System and Method for Warming a Person to Prevent or Treat Hypothermia”, commonly owned with this application.
The upper body thermal blanket 15 shown in FIGS. 1C and 1D is frequently used during thoracic, abdominal and pelvic surgery and/or in the post anesthesia care unit (PACU) to satisfy the need for therapeutic warming. As is known, a patient's core body temperature can drop to hypothermic levels quickly during surgery. To prevent or mitigate the effects of hypothermia, an upper body blanket may be deployed for therapeutic warming during the intraoperative period. However, the need for therapeutic warming often is ascertained only after surgery commences and it is inconvenient, and sometimes it is not possible, to interrupt attendance on a patient during a surgical procedure in order to locate and deploy a thermal blanket and bring it into operation. In such cases, therapeutic warming can be delayed until the patient enters the PACU, when the patient may have been hypothermic for a significant period of time. Given the frequency with which upper body thermal blankets are used during and after surgery, it would be very useful and clinically beneficial to conveniently position an upper body convective device with respect to a patient so that it could be quickly accessed and deployed during thoracic, abdominal, or pelvic surgery with little or no time spent in retrieval.
A warming device combining a clinical garment with a convective insert to provide comfort warming does not provide for therapeutic warming during thoracic surgery. Thus, even for a patient wearing a clinical garment with a convective apparatus as disclosed in WO 2003/086500, an upper body thermal blanket must be unpackaged, made ready and deployed during such surgery. Warming may be indicated postoperatively in order to stave off hypothermia while the patient's recuperation proceeds. Manifestly, a substantial convenience and a significant gain in a patient's physical condition would result from use of a warming device capable of clothing a patient preoperatively, while positioning a convective apparatus to therapeutically warm the patient during thoracic, abdominal, or pelvic surgery and postoperatively. Because of wide-spread and frequent use, it would be particularly desirable to have a multifunction warming device constituted of a clinical garment with a convective apparatus supported on the inside of the garment for easy deployment and use in warming a patient's upper body.
The assignee's Publication US 2006/0184217 published Aug. 17, 2006 discloses a warming device for perioperative use in which thermal blankets are attached to the inside surface of a clinical garment. However, use of the thermal blankets for therapeutically warming a patient wearing the clinical garment requires either that the thermal blanket be detached from the inside surface and repositioned for use, or that the clinical garment be removed from the patient and repositioned in order to correctly orient the thermal blanket with respect to the patient. In either case, the extra steps to access the thermal blanket for operation complicate use of the warming device, and consume time otherwise spent tending to the patient.
The deterrents to adoption of the warming device disclosed in US 2006/0184217 are eliminated by disposing an elongate convective thermal blanket for upper body use on the inside of the clinical garment, transversely to the garment, between its sleeves, with its permeable surface facing the patient. This positioning of the convective apparatus in the clinical garment locates it against the chest of a patient wearing the garment and permits it to be deployed and used on the patient during and after surgery without removal of the clinical garment from the patient, without removal of the convective apparatus from the gown, and without reorientation of the clinical garment in order to correctly orient the convective apparatus with respect to the patient.